First released in Line’s home market of Japan last August, Line Band become available worldwide in February. The company says the app now has over 15 million downloads — up from 5 million six months ago, and more than Path’s 10 million registered users — and it has marked the occasion by releasing Line Band 2.0. The smartphone apps have gotten a series of tweaks, including private messaging and search, while the service has branched out to desktops with PC and Mac clients.

Bands themselves are private social collections that function much like Facebook groups. They include a main messaging board, a gallery — for images, short video and even other documents; including MS Office file previews — a chat section and group calendar. A fifth section — ‘members’ — manages new invitations and who is in the Band.

Line says the PC clients are currently in beta, and offer a more basic version of the service, including bulletin boards, photos, and group chat. They currently support nine languages — Korean, English, Japanese, Chinese, Thai, Spanish, Indonesian, Malay and Vietnamese — with more to come when they exit beta before the end of 2013.

Mike Won, head of business development and global marketing at Line Band, spoke of the aim to increase uptake globally:

We are now aiming to acquire more users from the global market by resolving the problems that may result from the differences in mobile environments across countries. We have been reviewing user feedback from each market to provide better experiences in using our app and will continue to support global users.

The progress of Line Band demonstrates that the company is building a platform for mobile, beyond just a messaging app. The more services that it releases, the further it strengthens its ties with users to increase engagement and revenue opportunities.

With that in mind, we can probably expect Line Band to include paid-for stickers, other virtual content and more links to Line services soon.